1. Field of the Invention
The present invention relates, in general, to Near Field Communication (NFC) and, more particularly, to an external device for a mobile communication terminal, which enables non-contact NFC with the outside through an NFC unit, and an NFC method using the external device.
2. Related Art
The term “NFC” refers to a non-contact NFC technique that can transmit data at low power over a short distance through the application of a Radio Frequency Identification (RFID) technique using a frequency band of 13.56 MHz. NFC has been standardized chiefly by European Computer Manufacturers Association (ECMA) International. Nokia, Sony and Philips have participated in the standardization and commercialization of NFC.
When NFC is used, not only basic information, such as telephone numbers, but also data, such as Moving Picture Experts Group-½ Audio Layer 3 (MP3) files and photos, can be exchanged by bringing two or more terminals close to each other without any manipulation by a user.
Meanwhile, for use as a credit card or traffic card, there has been introduced a mobile communication terminal in which a module, to which a smart card can be attached, is included in the back of a mobile communication terminal body and an antenna is contained in a battery pack.
FIG. 1 is an exploded perspective view of a conventional mobile communication terminal.
Referring to FIG. 1, the conventional mobile communication terminal includes a mobile communication terminal body 110 and a battery pack 120.
The conventional mobile communication terminal body 110 is configured such that a smart card chip is attached to the back of the mobile communication terminal body 110. For example, a socket 111 corresponding to the chip specification of the smart card compliant with the ISO 7816 standard is formed in the back of the mobile communication terminal body 110.
When a smart card chip supporting a credit card or traffic card function is mounted in the socket 111 in the back of the mobile communication terminal body 110 and the battery pack 120 containing an antenna is attached to the mobile communication terminal body 110, the smart card chip and a baseband chip included in the mobile communication terminal body 110 communicate via the International Standards Organization (ISO) 7816 protocol, etc, analog signals from the smart card chip are transmitted to the antenna through connection terminals 113 and 121 between the mobile communication terminal body 110 and the battery pack 120, and analog signals received by the antenna are transmitted to the smart card chip through the connection terminals 113 and 121.
In general, antenna signals are high-frequency analog signals. The characteristic of the signal transfer between the smart card and the antenna is a very important factor that affects the characteristics of the antenna. Accordingly, when analog signals are transmitted/received between the smart card chip and the antenna through the connection terminals 113 and 121 between the mobile communication terminal body 110 and the battery pack 120, the signal transfer characteristic of the connection terminals 113 and 121 between the mobile communication terminal body 110 and the battery pack 120 must be appropriately maintained.
However, the connection terminals 121 of the battery pack 120 or the connection terminals 113 of the mobile communication terminal body 110 are covered with dust or worn away due to the frequent attachment and detachment of the battery pack 120, therefore the signal transfer characteristic of the connection terminals 113 and 121 may be significantly changed.
When the signal transfer characteristic of the connection terminals 113 and 121 between the mobile communication terminal body 110 and the battery pack 120 is significantly changed, signals received from the outside and signals transmitted to the outside through the antenna are distorted. Consequently, a serious problem in which the transactions of the traffic card or credit card through the smart card chip are erroneously performed may occur.
Furthermore, Korean Unexamined Patent Publication No. 2005-56779 discloses a portable storage device to be connected to a 24-pin socket included in a mobile communication terminal body. The disclosed portable storage device is only an external device that is simply connected to a mobile communication terminal and used as a portable storage device. However, the portable storage device never performs any NFC or Universal Serial Bus (USB) communication function.
Accordingly, there is an urgent need for a new external device for a mobile communication terminal, which does not change the characteristic of signals transmitted/received through the antenna despite the attachment and detachment of the battery pack to and from the mobile communication terminal, can be easily attached to a mobile communication terminal body, and enables USB communication with a USB host, and an NFC method using the external device.